U.S. patent application number 12/677848 was filed with the patent office on 2010-12-09 for electronic component, methods for the production thereof, and use thereof.
This patent application is currently assigned to KARLSRUHER INSTITUT FUER TECHNOLOGIE. Invention is credited to Horst Hahn.
Application Number | 20100308299 12/677848 |
Document ID | / |
Family ID | 39865672 |
Filed Date | 2010-12-09 |
United States Patent
Application |
20100308299 |
Kind Code |
A1 |
Hahn; Horst |
December 9, 2010 |
ELECTRONIC COMPONENT, METHODS FOR THE PRODUCTION THEREOF, AND USE
THEREOF
Abstract
An electronic component includes a first and a second electrode.
A layer of nanoparticles is disposed between the first and second
electrodes. The layer of nanoparticles includes an electrically
conducting compound of a metal and an element of Main Group VI of
the Periodic Table. A dimension of a majority of the nanoparticles
ranges from 0.1 to 10 times a screening length of the electrically
conductive compound. A dielectric layer has at least one common
interface with at least a part of the nanoparticles.
Inventors: |
Hahn; Horst;
(Seeheim-Jugenheim, DE) |
Correspondence
Address: |
LEYDIG, VOIT AND MAYER
TWO PRUDENTIAL PLAZA, SUITE 4900, 180 NORTH STETSON AVENUE
CHICAGO
IL
60601
US
|
Assignee: |
KARLSRUHER INSTITUT FUER
TECHNOLOGIE
Karlsruhe
DE
|
Family ID: |
39865672 |
Appl. No.: |
12/677848 |
Filed: |
August 20, 2008 |
PCT Filed: |
August 20, 2008 |
PCT NO: |
PCT/EP2008/006818 |
371 Date: |
March 12, 2010 |
Current U.S.
Class: |
257/9 ;
257/E21.09; 257/E29.068; 438/478; 977/773 |
Current CPC
Class: |
H01L 29/7869 20130101;
H01L 29/22 20130101; H01L 29/2203 20130101; H01L 29/76 20130101;
H01L 29/0665 20130101; H01L 29/78681 20130101; B82Y 10/00 20130101;
H01L 29/78696 20130101; H01L 29/4908 20130101 |
Class at
Publication: |
257/9 ; 438/478;
257/E29.068; 257/E21.09; 977/773 |
International
Class: |
H01L 29/12 20060101
H01L029/12; H01L 21/20 20060101 H01L021/20 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 12, 2007 |
DE |
10 2007 043 360.5 |
Claims
1-15. (canceled)
16. An electronic component comprising: a first and a second
electrode; a layer of nanoparticles disposed between the first and
second electrodes, the layer of nanoparticles including an
electrically conducting compound of a metal and an element of Main
Group VI of the Periodic Table, a dimension of a majority of the
nanoparticles ranging from 0.1 to 10 times a screening length of
the electrically conductive compound; and a dielectric layer having
at least one common interface with at least a part of the
nanoparticles.
17. The electronic component as recited in claim 16, wherein the
electrically conducting compound has a form of a planar
electrically conductive layer and the dielectric layer has a form
of a planar dielectric layer, the layer of nanoparticles has a form
of a planar structure and is disposed on the dielectric layer, and
wherein the dielectric layer is disposed on the planar electrically
conductive layer.
18. The electronic component as recited in claim 16, further
comprising an electrically insulating substrate and a control
electrode, and wherein the layer of nanoparticles is disposed on
the electrically insulating substrate and the dielectric layer is
disposed on a surface of the layer of nanoparticles so as to be in
direct contact with the control electrode.
19. The electronic component as recited in claim 16, wherein the
dielectric layer includes a solid or liquid electrolyte which,
together with the layer of nanoparticles, is configured to form an
interpenetrating network so as to be in direct contact with a
control electrode.
20. The electronic component as recited in claim 16, wherein the
layer of nanoparticles includes nanoparticles having a particle
size of from 5 nm to 500 nm and pores having a pore size
distribution of from 5 nm to 500 nm, the pores being disposed
between the nanoparticles within the disposed layer of
nanoparticles.
21. The electronic component as recited in claim 16, wherein the
nanoparticles include at least one of an electrically conductive
metal oxide, metal sulfide and metal selenide.
22. The electronic component as recited in claim 21, wherein the
nanoparticles include at least one of indium tin oxide, fluorine-
or antimony-doped tin(IV) oxide and aluminum-doped zinc oxide.
23. The electronic component as recited in claim 21, wherein the
nanoparticles include at least one of zinc oxide, titanium dioxide,
zinc sulfide and cadmium sulfide.
24. A method for producing an electronic component, the method
comprising: providing a first and a second electrode; disposing a
layer of nanoparticles between the first and second electrodes; and
providing a dielectric layer, wherein at least one of the providing
a first and a second electrode, the disposing a layer of
nanoparticles between the first and second electrodes, and the
providing a dielectric layer are preformed using a layer
preparation method.
25. The method as recited in claim 24, further comprising
performing a sintering step after the providing a first and a
second electrode, the disposing a layer of nanoparticles between
the first and second electrodes, and the providing a dielectric
layer are preformed using a layer preparation method.
26. A method for producing an electronic component, the method
comprising: providing a first and a second electrode; disposing a
layer of nanoparticles between the first and second electrodes; and
providing a dielectric layer, wherein at least one of the providing
a first and a second electrode, the disposing a layer of
nanoparticles between the first and second electrodes, and the
providing a dielectric layer are preformed using a layer
preparation method, and wherein the dielectric layer includes a
solid or liquid electrolyte which, together with the layer of
nanoparticles, is configured to form an interpenetrating network so
as to be in direct contact with a control electrode.
27. The method as recited in claim 26, wherein the nanoparticles
are dispersed in a liquid electrolyte, and further comprising
applying the nanoparticles to a substrate by spin coating or
printing.
28. The method as recited in claim 26, further comprising
performing an annealing step.
29. The method as recited in claim 27, wherein the liquid
electrolyte is configured to solidify after application thereof to
the substrate.
30. Method of making an electronic component useable as one or more
of a diode, a transistor, a voltage inverter and a sensor, the
method comprising: providing a first and a second electrode;
disposing a layer of nanoparticles between the first and second
electrodes; and providing a dielectric layer, wherein at least one
of the providing a first and a second electrode, the disposing a
layer of nanoparticles between the first and second electrodes, and
the providing a dielectric layer are preformed using a layer
preparation method so as to provide at least one of a diode, a
transistor, a voltage inverter and a sensor.
Description
CROSS REFERENCE TO PRIOR APPLICATIONS
[0001] This application is a U.S. National Phase application under
35 U.S.C. .sctn.371 of International Application No.
PCT/EP2008/006818, filed on Aug. 20, 2008 and which claims benefit
to German Patent Application No. 10 2007 043 360.5, filed on Sep.
12, 2007. The International Application was published in German on
Mar. 26, 2009 as WO 2009/036856 A1 under PCT Article 21(2).
FIELD
[0002] The present invention relates to an electronic component
including a layer of nanoparticles, a method for the production
thereof, and the use thereof.
BACKGROUND
[0003] In the recent years, it has been shown that it is possible
to tune the structural and functional properties of metallic
nanostructures in the form of thin films and nanoporous structures;
i.e., structures having an extremely high surface-to-volume
ratio.
[0004] The basic idea of the tunability of the electronic structure
and properties of nanocrystalline materials was first described by
H. Gleiter, J. Weissmuller, O. Wollersheim and R. Wurschum, and
published by them in Nanocrystalline Materials: A way to solids
with tunable electronic structures and properties?, Acta Mater. 49
(2001), 737-745.
[0005] DE 199 52 447 C1 and J. Weissmuller, R. N. Viswanath, D.
Kramer, P. Zimmer, R. Wurschum and H. Gleiter in Charge-Induced
Reversible Strain in a Metal, Science 300 (2003), 312-315, describe
that reversible length changes of nanoporous gold can be achieved
by accumulating electric charges at the interface of an electrolyte
with the metallic nanostructures in a double layer.
[0006] C. Bansal, S. Sarkar, A. K. Mishra, T. Abraham, C. Lemier
and H. Hahn described in Electronically tunable conductivity of a
nanoporous Au--Fe alloy, Scripta Materialia 56 (2007), 705-708,
that reversible changes in the electrical resistance of nanoporous
gold and nanoporous Au--Fe alloys can be achieved by accumulating
electric charges at the interface of an electrolyte with the
metallic nanostructures in a double layer. The changes in the
electrical resistance observed at applied charge densities of
approximately 50 .mu.C/cm.sup.2 were in the range of a few
percent.
[0007] In Electrically Tunable Resistance of a Metal, Phys. Rev.
Lett. 96 (2006), 156601, M. Sagmeister, U. Brossmann, S. Landgraf,
and R. Wurschum described the same effect at the same order of
magnitude for nanoporous Pt.
[0008] The concept of tunability of the electrical conductivity in
semiconductors, such as Si and Ge, which is known as "electric
field gating", has been established for decades and forms the basis
for their use in electronics. The basic structure consists in an
arrangement including a source and a drain coupled together by the
semiconducting material, and a gate electrode isolated from the
semiconductor by a suitable gate oxide. The conductivity of the
semiconducting layer can be varied over a wide range by a gate
voltage applied to the gate.
[0009] In the case of oxides, the region that can be influenced by
interface charges; i.e., the space charge region, is much larger
than in the above-mentioned metals, but smaller than in the case of
semiconductors, which have a lower charge carrier density than
conductive oxides. To date, however, hardly any studies have been
conducted on the use of oxides as tunable materials.
[0010] As regards the functional properties of conductive oxides,
R. Misra, M. McCarthy, and A. F. Hebard described the ability to
control the electrical conductivity of a thin indium oxide layer in
an ionic liquid, and to measure sheet impedance changes greater
than four orders of magnitude, in Electric field gating with ionic
liquids, Applied Physics Letters 90, (2007) 052905.
SUMMARY
[0011] An aspect of the present invention is to provide an
electronic component, a method for the production thereof, and the
use thereof, that will overcome the aforementioned disadvantages
and limitations.
[0012] Another, alternative aspect of the present invention is to
provide an electronic component which allows the electrical
resistance in a multiplicity of nanoporous structures to be
reversibly tuned over many orders of magnitude by applying a gate
voltage thereto.
[0013] In an embodiment, the present invention provides an
electronic component which includes a first and a second electrode.
A layer of nanoparticles is disposed between the first and second
electrodes. The layer of nanoparticles includes an electrically
conducting compound of a metal and an element of Main Group VI of
the Periodic Table. A dimension of a majority of the nanoparticles
ranges from 0.1 to 10 times a screening length of the electrically
conductive compound. A dielectric layer has at least one common
interface with at least a part of the nanoparticles.
DETAILED DESCRIPTION OF THE DRAWINGS
[0014] The present invention is described in greater detail below
on the basis of embodiments and of the drawings in which:
[0015] FIG. 1 shows prior art electronic components including a
conductive oxide a) without an electrolyte b) with an
electrolyte;
[0016] FIG. 2 shows an electronic component according to the
present invention including a layer of nanoparticles in the form of
a planar structure on a dielectric which is present in the form of
a planar dielectric layer;
[0017] FIG. 3 shows an electronic component according to the
present invention, in which the dielectric is located on the
surface layer of nanoparticles;
[0018] FIG. 4 shows an electronic component according to the
present invention, in which the dielectric is in the form of an
electrolyte which, together with the nanoparticles of the layer,
forms an interpenetrating network;
[0019] FIG. 5 illustrates the change in electrical resistance over
time of two electronic components according to the present
invention when varying the gate voltage;
[0020] FIG. 6 shows (a) current-voltage characteristics, (b) source
characteristics, and c) drain characteristics of an electric
component according to the present invention.
[0021] FIGS. 1a) and b) show electronic components which are known
from the prior art and which each include a semiconducting or
conducting metal oxide.
DETAILED DESCRIPTION
[0022] An electronic component according to the present invention
includes, firstly, two electrodes which act as source and drain for
the component.
[0023] A layer of nanoparticles is located between these two
electrodes, the nanoparticles being composed of an electrically
conducting or semiconducting compound of a metal and an element of
main group VI of the Periodic Table of the chemical elements, for
example, an oxide, a sulfide, or a selenide.
[0024] The dimensions of the majority of the nanoparticles range
should be between 0.1 times and 10 times the screening length of
the electrically conductive compound.
[0025] An electronic component according to the present invention
further includes a dielectric which has at least one common
interface with at least part of the nanoparticles of the layer.
[0026] The nanoparticles within the layer can have particles sizes
in the range of 5 nm to 500 nm. Located between the nanoparticles
within the layer are pores having a pore size distribution, for
example, in the range of 5 nm to 500 nm.
[0027] The nanoparticles can be composed of an electrically
conductive metal oxide, metal sulfide or metal selenide. Examples
include transparent conductive oxides, such as those of indium tin
oxide (ITO), fluorine-doped tin(IV) oxide (SnO.sub.2:F; PTO),
antimony-doped tin(IV) oxide (SnO.sub.2:Sb, ATO), or aluminum-doped
zinc oxide (AZO). Nanoparticles of zinc oxide, titanium dioxide,
zinc sulfide or cadmium sulfide can be used at elevated
temperatures.
[0028] In one specific embodiment, the nanoparticles are present in
the form of sintered nanoporous bulk structures, which were
sintered at moderate temperatures. The pore structure has distinct
grain boundaries/interfaces between the particles or grains of the
inorganic phase.
[0029] In another embodiment, the nanoparticles are present in the
form of loosely connected porous structures in which the interfaces
between contacting particles of the inorganic phase are not very
distinct.
[0030] In an embodiment of the present invention, the electronic
component of the present invention includes a layer of
nanoparticles which is deposited in the form of a planar structure
on the dielectric. The dielectric itself is in the form of a planar
dielectric layer which in turn is deposited on a planar
electrically conductive layer. Therefore, between the thin layer of
nanoparticles of the conducting or semiconducting compound and a
suitable electrolyte, planar interfaces are formed between the
compound and the dielectric.
[0031] In a further embodiment, the electronic component of the
present invention includes a layer of nanoparticles which is
deposited on an electrically insulating substrate. The dielectric
is located on the surface of the layer of nanoparticles and is in
direct contact with a control electrode. The dielectric (gate
dielectric layer) can, for example, be deposited in the form of a
dispersion and, therefore, conforms to the rough surface of the
functional layer. This ensures that the effect of the present
invention is also maximum for rough surfaces.
[0032] In a an embodiment of the present invention, the electronic
component includes a bi-continuous, interpenetrating composite
network which is composed of semiconducting or conducting
nanoparticles and a suitable electrolyte as a dielectric and which
forms a system of complex-shaped arbitrary interfaces between the
electrolyte and the individual nanoparticles. Here, too, the
dielectric is in contact with a control electrode. The electrolyte
itself may be present in a liquid or a solid phase.
[0033] By applying a potential, electric charges can be accumulated
at the interface between the electrolyte and the nanoparticles. The
electric charges are reversibly varied by changing the potential,
which allows the electrical conductivity of the layer of
nanoparticles to be reversibly changed. All surfaces of the
nanoparticles are in direct contact with the electrolyte, which
makes it possible to accumulate charges on all surfaces. In this
manner, a high effect can be achieved, allowing the layer to be
tuned over several orders of magnitude. The structure dimensions of
the nanoparticles should be of the order of magnitude of the
screening length to be able to vary the electrical conductivity of
the oxide phase to a noticeable degree.
[0034] In order to optimize the capacitances of the present
electronic component, only small surfaces should be used, such as
is also required in components. This allows the switching times of
the component to be kept to a minimum.
[0035] In order to operate the electronic component, a potential is
applied between the layer of nanoparticles and a counter-electrode.
This arrangement has already been implemented as an operational
unit, and the reversible change in the electrical conductivity
could be demonstrated over several orders of magnitude.
[0036] The structures of an electronic component according to the
present invention may be synthesized using conventional layer
preparation methods and subsequently covered with a liquid or solid
electrolyte (dielectric).
[0037] Suitable layer preparation methods include, for example:
[0038] (1) sputtering or vacuum evaporation methods; [0039] (2)
spin coating or printing methods, such as screen-printing methods
or ink-jet printing, of dispersions of the inorganic nanoparticles,
followed by a sintering step; [0040] (3) spin coating or printing
methods, such as screen-printing methods or ink-jet printing, of
electrolyte-containing dispersions of the inorganic nanoparticles,
followed by an annealing step.
[0041] In methods (1) and (2), after producing the layer and, if
necessary, performing a sintering or annealing step, the liquid or
solid electrolyte is applied as an additional layer to the thin
layer of the inorganic phase and subsequently provided with an
electrode having a large surface area.
[0042] In method (3), the nanoparticles of the inorganic phase are
directly dispersed in a liquid electrolyte and applied to a
suitable substrate by spin coating or printing, for example, screen
printing or ink-jet printing. This may be followed by an annealing
step that is compatible with the substrates used, the chosen
printing method and with the electrolyte and serves to achieve
optimum electrical conductivity across the interfaces of the
inorganic phase.
[0043] Instead of a liquid electrolyte, it is also possible to use
an electrolyte which is liquid prior to drying and solidifies when
dried. When using such an electrolyte, which solidifies when dried,
the shrinkage of the electrolyte phase may be used to draw the
inorganic nanoparticles together and thereby achieve higher
electrical conductivity.
[0044] Electronic components according to the present invention may
be used, for example, as diodes, transistors, voltage inverters or
as sensors.
[0045] The use of nanocrystalline functional particles composed of
a compound of a metal and an element of main group VI of the
Periodic Table, such as oxides, sulfides and selenides, in
combination with the use of the tunability of material properties
by reversible charging in an electrolyte, leads to new
possibilities for functional components in the field of printable
electronics. The use of a printable electrolyte/nanoparticle
mixture is suitable for printable electronics.
[0046] In the case of the electronic component shown in FIG. 1a), a
conducting metal oxide was deposited in the form of a thin oxide
film 20 on a dielectric layer 3 which acts as a gate and is applied
to a conductive electrode 4 made of highly-doped silicon or metal.
Electrodes 1, 2 for source and drain are directly deposited on
oxide film 20. The electrical conductivity of oxide film 20 is
varied by applying a gate voltage to dielectric layer 3.
[0047] In the case of the electronic component shown in FIG. 1b),
dielectric layer 3 of FIG. 1a), which acts as a gate, is replaced
by a solid or liquid electrolyte 30. Therefore, in place of
conductive electrode 4 (gate electrode), this component has a
control electrode 31, which should have a large surface area to
allow charges to be to transferred electrolyte 30 in the most rapid
manner possible. Here, too, electrodes 1, 2 for source and drain
are in direct contact with oxide film 20. The component is disposed
on an electrically non-conductive substrate 5.
[0048] FIGS. 2 through 4 show three embodiments of electronic
components according to the present invention, whose active layers
are each formed by a nanocrystalline oxide layer 10 composed of a
semiconducting or conducting metal oxide.
[0049] FIG. 2 shows an electronic component according to the
present invention. Here, an electrically conductive nanocrystalline
oxide layer 10 was applied by a printing method with or without
subsequent sintering to a dielectric layer 3 which acts as a gate
and is disposed on a conductive electrode 4 made of highly-doped
silicon or metal. Electrodes 1, 2 for source and drain are in
direct contact with nanocrystalline oxide layer 10. The electrical
conductivity of nanocrystalline layer 10 is varied by applying a
gate voltage to dielectric layer 3.
[0050] FIG. 3 shows another embodiment of an electronic component
according to the present invention. Here, electrically conductive
nanocrystalline oxide layer 10 is disposed on an electrically
non-conductive substrate 5 and is in direct contact with electrodes
1, 2 for source and drain. However, dielectric layer 3, which acts
as a gate, was deposited in the form of a dispersion on the surface
of nanocrystalline layer 10 and, therefore, conforms to the rough
surface of nanocrystalline layer 10. This ensures that the effect
underlying the present invention is also maximum for rough
surfaces. Dielectric layer 3 is in direct contact with a gate
electrode 31.
[0051] FIG. 4a) shows a particularly advantageous embodiment of a
component according to the present invention. Here, an electrically
conductive nanocrystalline oxide layer 10 is in direct contact with
electrodes 1, 2 for source and drain, and dielectric layer 3 of
FIG. 2, which acts as a gate, is replaced by a solid or liquid
electrolyte 30. Electrolyte 30 is in contact with a control
electrode 31. In this embodiment, too, the control electrode 31
must have a high surface area.
[0052] The change in the conductivity of nanocrystalline oxide
layer 10 is brought about by a low voltage between control
electrode 31 and nanocrystalline layer 10 between electrodes 1, 2
for source and drain. As exemplarily shown for positive charges in
the enlarged view of FIG. 4b), positive charges are induced at the
surfaces of the oxide particles. These charges are responsible for
the change in the conductivity of nanocrystalline oxide layer
10.
[0053] The structure exemplarily illustrated in FIG. 4 may be
produced by forming a nanoparticulate film 10 by printing,
especially screen-printing or ink-jet printing, between the two
electrodes 1, 2, which act as source and drain, by subsequently
sintering said film to create the conductive bridges between the
individual nanoparticles, and by then infiltrating said film with a
solid or liquid electrolyte 30. The element can then be switched by
applying a control voltage between electrodes 1, 2 for source and
drain and control electrode 31.
[0054] In an alternative embodiment, the nanoparticles are directly
dispersed in an electrolyte which is liquid at the time the
dispersion is made and during printing and which later either
solidifies or remains liquid. The dispersed nanoparticles are then
applied to a substrate in one step by a printing method. During the
printing and drying process, conductive contacts are created
between the nanoparticles of the conductive oxide, and, either
immediately or after moderate temperature treatment, the component
of the present invention is operational. This manufacturing method
is particularly suitable for use in printable electronics.
[0055] In FIG. 5, the electrical resistance of two different
components according to the present invention is shown as a
function of time as the control voltage applied between control
electrode 31 and electrically conductive nanocrystalline layer 10
as an electrode is varied between -0.3 V and +0.8 V (FIG. 5a)) and,
respectively, between -0.25 V and +0.85 V (FIG. 5b)). The variation
(scan) was performed at a rate of 0.5 mV/s. Both components were
configured according to FIG. 4. The measurement results show that
the electrical resistance of both components can be changed by a
factor of 350 (=35 000%; FIG. 5a) and, respectively, of 100 (=10
000%; FIG. 5b) by simply varying the control voltage. Consequently,
this effect is several orders of magnitude greater than the
reversible changes in the electrical resistance of nanoporous gold
and nanoporous Au--Fe alloys described by C. Bansal et al. in
Scripta Materialia 56 (2007), 705 ff.
[0056] FIG. 6a) shows the current-voltage characteristics of a
component according to the present invention, and demonstrates that
such component can be operated as a transistor.
[0057] FIG. 6b) and FIG. 6c) illustrate the source characteristics
and, respectively, the drain characteristics of a component
according to the present invention. A comparison of these two sets
of characteristics confirms that the effects illustrated in FIG. 5
do not originate from leakage currents between electrodes 1, 2.
[0058] The present invention is not limited to embodiments
described herein; reference should be had to the appended
claims.
* * * * *